Electrical control device



Jung 13,1939. I AVERY 2,162,237

ELECTRICAL CONTROL DEVICE Filed Nov. 27, 1936 2 Sheets-Sheet l FIE L INVENTOR. By Haro/d TAl e/y 0M ATTOR EY June 13, 1939. AVERY 2,162,237

ELECTRICAL CONTROL DEVICE Filed Nov. 27, 1936 2 She ets-Sheet 2 68. v INVENTOR.

by Haro/d 7/1 very 57 M/ Patented June 13, 1939' UNITED STATES PATENT OFFICE ELECTRICAL CONTROL DEVICE Application November 27,1936, Serial No. 112,897

lclaim.

trol devices and pertains more particularly to means for preventing rapid deterioration of electrical contacts which are subjected to frequent operation in such devices.

In such control devices as, for instance, electric motorgovernors of the general type disclosed in the patent to Ulrner, Number 1,795,240, issued March 3, 1931, which depend upon repeated open- ,10 mg and closing of contacts controlled by means responsive to motor speed to maintain the motor at a selected speed, it has been found that operation on direct rather than on alternating cur- .rent, deleteriously affects the contact surfaces, the contacton one side of the line pitting quite rapidly, and that on the other side of the. line building up.

It has been found practicable to prevent such deterioration of the contact surfaces by reversing the direction of current flow between such the present invention to provide a mechanism for effecting such reversal of the direction of current now as an incident to a normal operation 5 of any machine to which the control device is applied.

It is a further object of the invention to provide a circuit arrangement whereby the direction of current flow between control contacts may be reversed without effecting a reversal of the direction of-current flow through a motor to which current is supplied through said contacts, thus not only preventing short circuiting of the power: supply line where a polarity reversing switch of the type hereinafter described versal of a motor the direction of operation of which depends upon the direction of current flow therethrough.

vision of a circuit arrangement for the reversal of the direction of current flow through control contacts which will avoid any possibility of creating a short circuit across the main supply line, upon operation of said current reversing means while the respectivecircuits are enera I i A further object of the invention is the provision of an efllcient and economically designed switch mechanism for the foregoing purposes. and actuating devices-for the same whereby the frequency of thev reversals of the direction of current flow may, if desired, be reduced in numher as compared-with the number of initiations contact faces at intervals, and it is an object of is 'used, but also making it possible to avoid re- A further object of the invention is the pro- The present invention relates to electrical con-.

of the operation of a machine of which they form 'apart.

Other Objects and advantages of the present invention will appear from-the following description of a specific embodiment thereof, reference 5 being had to the accompanying drawings forming a part of this specification in which:

Figure 1 is a detail view in side elevation of a reversing switch embodying the present invention, and of the actuating devices therefor; 10

Figure 2 is a-circuit diagram;

Figure 3 is a view in side elevation of a preferred form ofreversing switch embodying the present invention;

Figure 4 is a view in plan thereof; IF

Figure 5 is a view inelevation of said switch, with certain parts removed to show details. of the construction of the contact segments;

Figure 6 is a detail view of one of the contact segments and an element of the operating means Q therefor;

.Figure 7 is a view in elevation of said switch, with the contact segments also removed to show the arrangement and construction of the brush elements; I

I Figure 8 is a sectional view taken on the line l8 of Fil e 3; and

Figure 9 is a detail, perspective view of one of the brush elements. I

In the accompanying drawings the invention .0 is shown as applied to a calculating machine of the character described in Swiss Patent No. 183,500 issued April 15, 1936 corresponding, in all pertinent matters, to the copending United States application of Harold T. Avery, Serial 5 4 Number 102,949, filed December 18, 1933, driven by is governed motor of the type above described. It is not necessary that the direction of current flow through the control contacts be reversed at extremely frequent intervals in order m to prevent deterioration of the character hereinbefore described, and it would, in fact, be sufficient if such reversal of the direction of current flow were effected at approximately halfhour intervals in the course of the machine's operation. Since more frequent reversals are unnecessary, the wear incident to operation of any current reversing device may be substantially reduced by connecting it to the machine in such a manner as to effect its operation as inm frequently as is consistent with automatic operation thereof by the machine, without special attention by the operator.

In the calculating machine above referred to, the setting clutch shaft I, shown in Figure 1 be less satisfactory for the purpose.

of the present disclosure, is rotated 180 at the commencement of machine operation; and is thereafter held stationary even though other parts of the machine may continue to operate under power from'the motor for avplurality of cycles thereafter. Mounted on this shaft 4IIJ in the machine as described in the above mentioned application, are cams 226 and 22! which, through rollers 222 and 223, are adapted to rock a cam follower 224 to impart a leftward oscillation through link 226 to shaft 2i! supported on member 2 'pivotaily mounted on shaft 2|6, each time shaft I is rotated 180.

Since these parts are infrequently operated, yet are'inevitably operated during the normal use of the calculating machine, they are particularly adapted for operating the. switch of the present invention. It will be understood, however, that any more frequently operated parts of the machine might-be used, although they would Freely mounted on shaft 2|; is an arm II, the remote end of which is provided with a turned lug II which serves as anactuating tooth for the ratchet wheel. i6. An extension' l6 on the end of arm-H projects between the ratchet wheel l6 and the plate I! to prevent lateral disengagement from the ratchet wheel of the tooth l3; while stud 2! on the frame of the machine serves to prevent the tooth it from rising out of engagement with the ratchet wheel IS, the arm being'contoured adjacent the stud 2| to permit the normal p rating movement of arm II to advance ratchet wheel .bushing 24 passed through said plates and said disk is provided with a shoulder 26 adjacent plate I! and an offset 26 adapted to be spun to overlie a portion of plate i6, thus holding the said plates and disk in assembled relationship.

The portions of the plates "and I6 remote from the bushing 24 are maintained in properly spaced relationship by a plurality of spacers 21 having extensions 29 adapted to fit snugly within holes in the plates. The spacers 21 are also preferably provided with apertures- 29 through which bolts or the like may be passed to secure the switch to the frame of a machine.

Ratchet wheel I is fixed upon a shaft II as,

,for instance, by riveting over the end of the shaft at 33,. and said shaft is rotatably mounted in the bushing", above described. The end of the shaft 91 remote from ratchet wheel II is reduced in diameter providing a shoulder II, and upon the reduced portion of the said shaft. are received/an insulating dkc 46 (see-also Figure 7), the commutator segment disc assembly 46 (see also Figures'S and 6), and a second insulating disc 41.

As shown in'Figures 5 and 6, the commutator segment disc assembly 46 comprises a pair 01'- identical metallic commutator segments 49 and a retainer-therefor consisting of a member 6|,

of insulating material, having lobesfllL-fltflng complementary-recesses 66 of the segments 49, to provide a dovetail keyed connection, andalso 5 having projections 61 extending between the sea ments 49 to space them from each other. T

Members fl, 6|, and 4'! are received upon the reduced end of shaft 3| and secured tberetoby means such as nut II which compresses lock washer 63 to press the aforementioned elements flrmlyagainst shoulder 4| of shaft, ii. The three elements are thus constrained to rotate with the shaft 3|, segment 49 having a dovetail keyed connection with the member 6| as aforesaid, and being restrained against lateral displacement with respect thereto by the insulating discs 49 and 41..

Rockably mounted with respect to plates I I and 16 are four brushes 65 adapted to make electrical contact with the two commutator segments 49. Each of these brushes, as shown in detail in Figure 9, is formed with an electrical contacting face 66, a connection lug 61, and an offset end 66, whereby the brush may be rockably mounted by inserting said end through a slot 16 in plate 16 so that it extends between the plates I! and 46. Preferably the opposite end 'of the brush is also providedwith a swedged projection 69 adaptedto serve as a spring anchor, as hereinafter described.

Each of thebrushes 65 is thus mounted, as. best shown in Figure 4, with its offset end 69 projecting through one of the four slots 19 of plate i6 and rockably contacting the plate H. A spring I3, compressed between the spring anchor projection 69 and the plate l1 and passing through an aperture in plate l6, maintains the contact face 66 of each brush pressed against one of the contact segments 49.

To prevent excessive wear between the contact brushes 66 and segments 49, and at the same time insure the maintenance of good electrical contact between-them, each of the segments 49 is preferably provided with a plurality of apertures 16 filled with a conductive lubricant such as graphite,

There may be suflicient friction between the brushes 65 and the contact segments 49 to prevent movement of the segments with respect to the brushes during the retraction of theoperating arm Ii toengage a new tooth of the ratchet wheel i5. However, additional means for frictlonally resisting rotation of the shaft II in order to prevent such movement, may be provided in the form of a spring washer H compressed between the ratchet wheel l6 and the end of the bushing 24.

' It will be observed that as the gap between segments 49 passes under a brush 65, one brush 66 may momentarily contact both of the segments 49, and thus, if the switch were disposed in the main current supply circuit so as to effect a reversal of the direction of current flow through the motor proper, as well as through the governor contacts, a momentary short circuit would be produced across themain'current supply line which -might result in substantial damage; The present invention therefore contemplates disposing the above described reversing switch in the circuit of a governed motor or similar device so as to eifect reversal of the direction of current flow through the make and break contacts of the motor governor without reversing the direction of current supply through the motor itself; In this way there can be no danger of short circuiting the main supply line even momentarily, since the effect of a brush 66 contacting both of the segments" will be merely to shunt out the make and break contacts of the motor governor and cause" a momentary speeding up of the motor without any deleterious effects whatever.

It is desirable, however, in installing the reversingswitch to make sure that an operation or the warm Ii may carryone segment-"49 completely out 

